The animation system inserts the key frame into tiles.png

[grunt-lucas]

This is not a bug per-se. But it's not intuitive. Since they key frame is never actually displayed in-game, we shouldn't insert it into an in-game asset. Additionally, we should modify the compilation code so that the colors in the key frame are not actually assigned to a palette. In most cases, this won't actually matter, since users are probably using a duplicate of 00.png for their key frame. However, some advanced users may want to use custom key frames with exotic colors, and Porytiles shouldn't force them to have a suboptimal palette allocation in this case.